M Nafti, Z Khaldi*, B Rekik and A Ben Gara

Abstract

Goats are well adapted
to Tunisian climatic conditions. Goat breeding is primarily found in the
mountains, natural- pasture regions, and the arid (Sahara) and oasis regions in
the south of the country. Goat variability is high in Tunisia and breeds are
under extensive production systems. The objective of this study was the
identification and phenotypic characterisation of various goat breeds or
populations in the oasis in six localities in the governorate of Tozeur.
Qualitative and quantitative traits of horns (form and length), the coat, ears,
hair, teeth, the cutting, etc. were used to distinguish among phenotypes
representing sub- populations of goats.

There were four locally
identified goat populations. The first population called “Arbi” is characterised
by a long black to black and white coat with frequently shammy, generally with
bears but without wattles. The second population called “Cherki” has
short-hair-coat coloured with several colours often shammy. The third population
is the “Damasquine”. The latter includes animals that are high on their paws
showing greater features than the two first populations. Finally, the “Alpine”
with her specific shammy colour and is made of animals that are too high on
their paws compared to other populations. Morphological differences among
various populations indicate high diversity of goats in the Tunisian oasis. This
study may be complemented by molecular characterisation of various populations
for conservation and genetic improvement schemes.

Key words: locality, phenotype, polymorphism, population

Introduction

The goat population in Tunisia counted 1412000 live animals in 2004, among of
which 809330 were females. Female population size increased up to 820000 in
2006, with a growth rate of 1.2% (Ministry of
Agriculture and Hydraulic Resources 2006). The abundance of goats mirrors the increase of aridity from
the north to the south of the country. Goats in Tunisia represent a high
diversity and heterogeneity, which is the result of uncontrolled brewing among
various breeds populating different areas in the country. Therefore, it is
difficult to distinguish among well-defined genetic entities. The study of the
features and the productive behaviour of a population are of considerable
utility, especially, when animal resources display some authentic details,
biologic, technical or environmental (Narjisse et al 1989). The characterization
of local goats, raised in the arid Tunisian regions, presents scientific and
technical interests especially to the genetic improvement and also to the
conservation of animal genetic resources. The aim of this study was to
characterize goats in the Tozeur region, in the south of Tunisia, on their
morphological appearances and to link morphological characteristics to genetic
determinism and environment.

Materials and methods

Survey

Our study took place in 6
localities (El Hamma, Tozeur, Degueche, Ibn Chabbat, Legwifla and Nefta) in the
region of Tozeur. The choice of the localities within the whole region was fully
developed according to the importance and sizes of herds. For instance, herds
with at least ten animals were privileged especially when they included
two-year-old females. This approach is justified by the fact that female goats
spend more time in the herd than males. A total of 36 herds were surveyed and
sampled animals were 450 females and 38 males.

Trait definition and measures

The genetic profiling was done
following the standards found in Lauvergne (1986), Cogovica (1987) and Lauvergne
et al (1987). Those standards recommend various scales such as form and length
of horns, colour pattern, dentition, the length of the coat, length and carriage
of the ear, etc. Phenotypes that are qualitative in nature were marked in terms
of presence or absence while quantitative variables were measured.

Analysis

Univariate analysis of quantitative and qualitative profiles

Data were organised in a I x J
contingency table, where the I (line) represents observations and J (column)
represents traits. Then, Xij is the ith
observation on the jth trait. Elementary statistics (mean, standard
deviation, frequencies, etc.) and distributions of quantitative measures of
various traits were determined. Firstly, we studied the representativeness index
of the total value (Table 1). Secondly, attributes (qualitative measures) were
analysed according to norms defined by Lauvergne (1986) and Cogovica (1987).
Absolute frequencies of phenotypes were determined in each locality. These
frequencies were complemented by relative gene frequencies coding for the
observed phenotypes with presumably established genetic determinism.

Table 1.
Descriptive statistics of quantitative variables for the goat
population in the Tozeur region

Parameter

Body length

Wither height

Heart girth

Ears length

Hairs length

Horns length

N

488

488

488

488

488

403

Mean

96.7

67.0

75.8

17.9

7.78

22.9

STD

9.18

5.68

6.78

2.80

4.53

7.44

Variance

84.5

32.3

46.0

7.84

20.5

55.4

Minimum

79.0

52.0

59.0

6.00

1.50

7.00

Maximum

127

93.0

104

34.0

22.0

58.0

CV

9.50

8.49

8.94

15.6

58.2

32.5

Mode

104

69.0

75.0

19.0

3.00

21.0

Median

96.0

67.0

75.0

18.0

7.00

22.0

Inferior quantile

89.3

63.0

71.0

16.0

3.50

18.0

Upper quantile

103

70.0

79.0

19.0

12.0

26.0

Range

48.0

41.0

45.0

28.0

20.5

58.0

Multivariate analysis

The methods of studying whole
characters rest on the principles of multi-dimensional analysis (Jivotovski
1985). Multivariate analyses were used to determine relationships among various
variables. A principal component analysis was performed on the quantitative
variables: the cutting, the wither height, the turn of the cannon, the ears
length, the horns length and the length of the hairs. Axes were intended to
represent various breeds or populations through specific common observables
characters. A general linear model (SAS 1989) was then used to explain the
variation of observed characters (body length, wither height, heart girth, earslength, horns length, hair length) by explanatory
variables such as locality, breed, sex, age, etc. The general form of the linear
model was:

Results

Descriptive statistics for quantitative characters

The largest recorded value of the range was for the length of
the horns which was 58 cm (Table 1). The coefficient of variation was less than
10% for the wither height, the heart girth and the cutting and was equal to
15.6% for the ears length (Table 1). However, for the horns length, this
coefficient reached 32% and was up to 58.2% for the hairs length. The average
body length of sampled animals varied from a locality to another (Table 2). The
highest value was observed in Nefta (mean = 104.2, STD = 10.1) while the lowest
value was observed in El Hamma (mean = 92.6 cm, STD = 9.4 cm). We could identify
two classes of height, the first with a mean height around 65 cm in Degueche, El
Hamma and Tozeur localities and the second around 68 cm in Ibn Chabbat, Legwifla
and Nefta localities. On the other hand, in Nefta, Legwifla and Ibn Chabbat we
recorded large means of heart (76 cm < mean < 80 cm) compared to that found in
other localities with the lowest value found in El Hamma (72.9, STD = 5.8 cm).
Important ear length differences were also observed among the different
localities. The longest ears were found in Nefta (19.2 cm). As for the length of
horns (for horned animals only), Legwifla and Ibn Chabbat had the largest means.
The long hairs distinguish the localities of Legwifla and Ibn Chabbat localities
among the others, while animals in Nefta and Degueche localities had the
shortest hair lengths.

Table 2. Average
values (in cm) of quantitative variables for the goat population in
the Tozeur region.

Locality

Body length

Wither height

Heart girth

Ears length

Hairs length

Horns length

El Hamma

92.6 (9.37)

65.0 (5.06)

73.0 (5.8)

17.7 (2.5)

15.9(10.7)

6.75 (3.7)

Tozeur

97.4 (8.24)

64.8 (4.02)

74.4 (4.9)

17.6 (2.7)

17.7 (11.8)

5.29 (3.3)

Degueche

98.5 (8.89)

65.9 (4.71)

74.9 (5.9)

16.8 (2.4)

18.9 (10.89)

4.2 (2.5)

Ibn Chabbat

99.6 (6.82)

68.2 ( 4.81)

77.4 (6)

18.6 (2.08)

22.3 (10.4)

9.22 (4.1)

Legwifla

95.4 (8.5)

68.1 ( 6.34)

76.6 (6.3)

17.8 (2.7)

20.3 (9.4)

10.3 (4.4)

Nefta

104 (10.08)

68.8 (6.27)

79.8 (8.7)

19.2 (4.55)

15.8 (15.4)

4.18 (3.3)

(.): Standard deviation

Nature of phenotypic
frequencies

The visible phenotypic
profile

Frequencies of observable
phenotypes tended towards one. The obedient characters to this tendency were the
normal length ears, the presence of the horns, the absence of the wattles and
the straight chamfer. The sites of Tozeur, Ibn Chabbat and Legwifla were good
examples of that tendency.

The genetic profile

The genetic profile was deduced
directly from the phenotypic frequencies. Derived allelic frequencies are given
in Table 3. These frequencies show the dominance of the wild character which
supposes that the studied goat populations belong to the traditional type
according to Lauvergne (1986). Principally normal length ears, the presence of
horns, the absence of the wattles, the absence of the beard and the relatively
short hairs characterize the goat populations of the Tozeur area.

The locus « length of the
hairs » (HL)

A pair of autosomal alleles
controls the length of the hairs with intermediate dominance of the short hair
HL+ in relation to the HLL gene with long hairs (Lauvergne
et al 1987, Pattie and Restall 1989).
In this study, we observed a greater proportion of the long-haired animals HL,
with 57% of HLL and 43% of HL+. Similar results were
reported by Lanari et al (2003) with proportion 53% and 47% for long and short
hairs, respectively, in Criollo goat population.

The locus «wattles presence»
(Wa)

The presence of the wattles is
controlled by a dominant autosomal gene (Waw) (Lauvergne 1987).
The presence of wattles on the neck is dominant and is common in some strains of
feral and milking goat (Pattie and Restall 1989). But in
this study, the absence of wattles dominates with the
wild allele Wa+ and an allelic frequency nearing 0.86.

The locus «presence of horns»
(Ho)

The polled character (HOp)
is an autosomal gene bound to the sex. In the homozygous state, HOp
exercises a pleitropic action leading to partial or total sterility (French
1971, Dolling 1999, Pattie and Restall 1989; Vivicorsi
1998). About 83% do not have horns, therefore threatened by the inter-sexuality
or sterility.

The locus «beard presence »
(Br)

The beard is controlled by the
autosomal allele Br bound to the sex, dominating in males and recessive in
females (Lauvergne 1987). The greatest portion of the studied populations do not
have beards (60%), similar results were presented by Vivicorsi (1998) in the
French Rove goats.

Table 3. Genetic
profile of the local goat populations in the Tozeur region

Name of locus

Alleles

Allelic frequencies

Name

Symbol

Ear length

Wild

Reduced

EL+

EL

0.89

0.11

Horns

Wild

Polled

HO+

Hop

0.83

0.17

Wattles

Wild

Wattled

Wa+

Waw

0.86

0.14

Beard

Wild

Bearded

Br+

Brb

0.60

0.40

Hair Length

Wild

Long

HL+

HLL

0.43

0.57

Classification of local goats on quantitative characters

Large phenotypic correlations
(Table 4) were found between heart girth and wither height (0.84), heart girth
and length of the horns (0.73), body length and heart girth (0.69) and wither
height and body length (0.64). However, ears length and hairs length were not
highly correlated. The lowest correlation coefficient (0.10) was found between
body length and hairs length. Similar results were reported by
Pattie and Restall (1989) on Australian goat populations.
The principal component analysis revealed distinct populations. The first
component was represented by the wither height, heart girth and body length; the
second component by the hairs length and finally the third component by the ears
length. These components may be representative of four populations: the first
one represents “Arbi goats”, the second “Serti goats” (a combination of “Cherki”
and “Malti” breeds) and the third may represent both “Damasquine” and “alpine”
breeds.

Table 4. Correlations among
quantitative variables for the goat population in the Tozeur region

Variable

Body length

Wither height

Heart girth

Ears length

Horns length

Hairs length

Body length

1

0.64

0.69

0.34

0.61

0.10

Wither height

0.64

1.00

0.84

0.33

0.62

0.26

Heart girth

0.69

0.84

1.00

0.33

0.73

0.24

Ears-length

0.34

0.33

0.33

1.00

0.22

0.21

Horns length

0.61

0.62

0.73

0.22

1.00

0.23

Hairs-length

0.10

0.26

0.24

0.21

0.23

1.00

Classification of local goats on qualitative characters

Local goat populations can be
divided into: The Cherki goat that results essentially from melting of the Malti
and Arbi breeds. The close-cropped hairs (92.4%) with ears of all forms
characterize this goat population. The intermediary form of horns was abundant
(76%); polled animals represent 20% of this population. All possible hair
colours exist within this population with the dominance of the shammy colour.
Neither wattles nor beards generally exist and the straight head form is common
in Cherki goats. The black-long-haired animals constitute 66.5% of Arbi goats.
The ears form is the falling in 80% of the cases. The horns are often present
with 72% of intermediate form. The wattles are absent in 87% of the population.
The presence or the absence of the beard has an equal percentage. The chamfer is
straight for 76% of this population and the concave form of the chamfer was
rarely found. The Malti goat presents characters very close to those of the
Cherki population. The coat is predominantly close-cropped (80%) and the rest
are medium-length coats (20%). A dominance of the shammy colour (80%) was
noticed. The Damasquine goat, that is either pure breed or crossed with the
local goat, possess long falling ears (80%). Several colours exist within this
breed with a dominance of the reddish colour. The wattles are quasi-absent and
the beards are almost absent (in more than 70% of the cases). The chamfers
concave type is absent and the straight type represents 60% in this population.
All Alpine goats have close-cropped coat, 85.5% of animals with trained ears,
63% present ibex form of horns and 91% with shammy’s hairs. The wattles and the
beards are absent (in more than 75% of cases). The chamfers are straight and
concave.

Description of identified goat populations

Arbi population

This population is characterized
by a black, black and white coat, sometimes shammy, grey or white. Their hairs
are essentially long with means of 11.5 cm for males and 10.2 cm for females.
The ears form is falling. The chamfer is straight and the head has horns of 18.8
cm of length for males and 18.1 cm for females. The measurements at the
tourniquet are around 75 cm for males and 66.7 cm for females. Males have a
heart girth of 84.2 cm and that of females is equal to 75.3 cm. The mean body
length of males of this breed is 104.2 cm while that of females is around 95.8
cm.

Serti population

It contains the two Cherki and
Malti breeds having similar features. The profile of the head is straight to
concave. Its coat is multicoloured, frequently shammy. All forms of ears have
been recorded; the head is horned, generally without neither bears nor wattles.
The hair is close-cropped. The recorded measurements of body length were 96 cm
and 93.7 cm for males and females, respectively. The heights at the tourniquet
of males were close to 64 cm in males and 65 cm in females. Measured heart
girths were of 73 cm for both sexes who also have similar ear lengths.

Damasquine population

It has features of the native
breed and exotic goats. Animals of this population present different types of
hair with a dominating close-cropped type. The ears are broad, long and falling.
The colours of the hairs are variable. The beard and the wattles are absent in
the majority of animals. Mean body length was 127cm and 106.2 cm for males and
females, respectively. Heights at the tourniquet are around 87 cm in males and
68.2 cm in females, while heart girths reached 101 cm and 83cm in males and
females, respectively.

Alpine population

Specific features distinguish
this population. Hairs are of the close-cropped type, ears are trained and
sometimes stalked, and the ibex form of horns is dominating. Wattles and beards
are generally absent. The height at the tourniquet was 80 cm, the heart girth
was more than 96.6 cm and body length was 117.5 cm in males; respective measures
in females were 68, 76.7 and 104 cm.

Variation of quantitative variables

Identified breeds or
populations, sex and age of the goat and locality (Table 5) were used to explain
variation of quantitative variables (body length; wither height, thoracic
perimeter, ears length, hairs length and the horns length). The coefficient of
determination (R²) ranged from 28.6 % for ears length to 64% for hairs length.
All variables varied with the breed (p< 0.05). The locality was also an
important source of variation for most of the studied variables except for hairs
and horns lengths.

Conclusion

Goat populations in the Tozeur
region showed a high polymorphism. This polymorphism results from the
introduction of exotic breeds and also mirrors breeding management in the
region. Although local farmers distinguish only between two breeds Arbi and
Cherki according to the unique criterion length of the hair, four distinct
breeds Serti, Arbi, Damasquine and Alpine were found in the region. This work
may constitute the basis for microsatellite studies to help implementing breeding strategies for the genetic
improvement and conservation of Tunisian goat populations